An apparatus described in JP-10-220272A (U.S. Pat. No. 6,142,121) is proposed as an apparatus of this kind. In a common-rail type fuel injection system constructed of this fuel injection apparatus, fuel pressure-fed from a fuel pump is accumulated in a high-pressure state by a common-rail. Then, the accumulated high-pressure fuel is supplied to the fuel injector of each cylinder through pipes (high-pressure fuel passage) disposed for each cylinder. The common-rail is provided with a specified pressure sensor (rail pressure sensor). This system is constructed in such a way as to control the driving of various devices constructing a fuel supply system on the basis of the output of the sensor from this rail pressure sensor.
In recent years, the need for improving exhaust emission is increasing in a diesel engine for an automobile. A study has been conducted in order to improve accuracy of a fuel pressure control. Under the present circumstances, the fuel supplied to the fuel injector is controlled by adjusting the fuel quantity supplied from the fuel pump to the common-rail according to the engine operation condition of each time.
However, if an error arises in the fuel quantity supplied to the common-rail from the fuel pump, an error arises also in the fuel pressure in the fuel injector, which may deteriorate an exhaust emission. In the fuel pump which has a plurality of plungers for pumping the fuel, an error may arise in fuel pumping quantity for every plunger, which may cause an error in pressure of the fuel supplied to the fuel injector.